1. Field of the Invention
The present invention relates to a process for purifying allyl alcohol. More particularly, the present invention relates to a process for obtaining allyl alcohol having a high purity by efficiently removing water from an aqueous solution of allyl alcohol.
2. Description of the Related Art
Allyl alcohol is an industrially valuable substance used for the synthesis of various chemicals such as glycerol and diallyl phthalate and as an intermediate for the synthesis of synthetic resins.
As the process for preparing allyl alcohol, there is known a process in which, as indicated by the following reaction formulae (1) and (2), allyl chloride is formed by high-temperature chlorination of propylene and allyl chloride is subjected to alkali hydrolysis: EQU CH.sub.2 .dbd.CHCH.sub.3 +Cl.sub.2 .fwdarw.CH.sub.2 .dbd.CHCH.sub.2 Cl.sub.2 +HCl (1) EQU CH.sub.2 .dbd.CHCH.sub.2 Cl+NaOH.fwdarw.CH.sub.2 .dbd.CHCH.sub.2 OH+NaCl (2)
This process is defective in that expensive chlorine should be used in a large amount and since hydrogen chloride gas is handled, corrosion of apparatus is serious.
Another process is known in which allyl alcohol is prepared by isomerization of propylene oxide using lithium phosphate as a catalyst: ##STR1##
This process is also defective in that the starting material is expensive.
Recently, there has been proposed a process in which propylene is used as the starting material and allyl alcohol is prepared without handling chlorine or hydrogen chloride. According to this process, as indicated by the following formulae (3) and (4), propylene is reacted in the presence of acetic acid with oxygen or an oxygen-containing gas by using a catalyst comprising an alkaliacetate and palladium, optionally together with a copper compound, supported on a carrier, in the gas phase, at 100.degree. to 300.degree. C. and 0 to 30 atmospheres (gauge pressure), to obtain allyl acetate, formed allyl acetate is collected by cooling, an aqueous solution of acetic acid is added to collected allyl acetate to form a homogeneous solution, the homogeneous solution is passed through a tubular reaction vessel filled with a strong-acid cation-exchange resin and heated by a heating medium, and the reaction liquid is subjected to distillation to obtain allyl alcohol [see, Japanese Unexamined Patent Publication (Kokai) No. 60-32747 and Japanese Unexamined Patent Publication (Kokai) No. 60-258171]: EQU CH.sub.2 .dbd.CH--CH.sub.3 +AcOH+1/2O.sub.2 .fwdarw.CH.sub.2 .dbd.CH-CH--CH.sub.2 OAc+H.sub.2 O (4) EQU CH.sub.2 .dbd.CH--CH.sub.2 OAc+H.sub.2 O.fwdarw.CH.sub.2 .dbd.CH--CH.sub.2 OH+AcOH (5)
According to this preparation process, allyl alcohol is obtained in the form of an aqueous solution. However, since allyl alcohol (having a boiling point of 96.degree. to 97.degree. C.) forms an azeotropic mixture (having a boiling point of 87.5.degree. C.) with water, water cannot be removed only by distillation.